1. Field
The present invention relates generally to the fabrication of semiconductor devices and, more specifically, to improving adhesion between low dielectric constant films and chemical vapor deposition (CVD) films (for example, films made of silicon dioxide, silicon carbide or silicon nitride) that are deposited on top of the low dielectric constant films.
2. Description of the Related Art
Fabrication of integrated circuits (ICs) to improve performance and reduce costs involves a complex analysis of materials properties, processing technology and IC design. ICs consist of multiple layers of conducting, insulating and semiconducting materials, interconnected in various ways by conducting channels and plugs, including various dopants implanted into the IC for producing the desired electronic functionality. Insulating or dielectric layers are used to provide electrical isolation for current-carrying elements of the IC. Such layers are typically referred to as xe2x80x9cinterlayer dielectricsxe2x80x9d or ILDs.
The near-universal trend in the manufacture of integrated circuits is to increase the density of components fabricated onto a given area of wafer, increase the performance and reliability of the ICs, and to manufacture the ICs at lower cost with less waste and fewer defective products generated during the manufacturing process. Increasing component density involves reducing the minimum feature size of the IC including decreasing the spacing between conductors. However, as the spacing between conductors decreases, the possibility of crosstalk and capacitive coupling between conductors increases. Thus, there is a need to decrease the dielectric constant (K) of the insulating material between conductors of the IC, thereby reducing capacitive coupling and crosstalk.
Typical dielectric materials used in present ICs include silicon dioxide, silicon nitride, and cured silsequioxanes. Silicon dioxide has been a popular dielectric since, among other properties, it possesses mechanical and thermal properties to withstand typical semiconductor manufacturing processing steps. However, the dielectric constants of these materials range from approximately 3.0 to approximately 7.0 (or higher) which is not adequate for the performance of future ICs. The speed of operation of future ICs is likely to be limited by RC (resistance-capacitance) delay in the conducting interconnects. Thus, it is desirable to employ a material for the ILDs having low dielectric constants (low-K) thereby permitting a higher density of components to be fabricated on the IC without detrimental electrical effects.
Thin films are typically deposited on the IC by chemical vapor deposition (CVD) or spin-on, which are two widely used processes in the semiconductor industry. In one common scheme, a low-K film is deposited by spin-on deposition, followed by deposition of a CVD cap layer. One drawback of low-K ILD films is the poor adhesion between the low-K films and CVD layers deposited onto the low-K films. Known methods to improve the adhesion characteristics involve some type of in situ plasma pretreatment to chemically modify the surface of the low-K dielectric. For example, ammonia, hydrogen, and nitrogen plasmas will all act as reducing agents that have proven beneficial for some films. An oxygen plasma will strip hydrocarbon impurities from the surface, and this has also proven somewhat beneficial.
There remains a need to compensate for the inadequate adhesion qualities of low-K films. There is a further need to improve the adhesion characteristics of the low-K film without significantly increasing the overall K of the resulting film.
The present disclosure is directed to apparatus and corresponding methods for improving adhesion between silicalite-plus-binder dielectric films (herein after referred to as xe2x80x9csilicalite filmsxe2x80x9d) and CVD films deposited on top of the silicalite films. The silicalite film is modified to enhance the adhesion of films subsequently deposited over the silicalite film by depositing a layer of silicalite having an enriched concentration of binder above the standard silicalite film. The additional layer of silicalite having the enriched concentration of binder greatly improves the adhesion characteristics of the total xe2x80x9cstackxe2x80x9d of the standard silicalite film and the binder-enriched film without significantly increasing the overall K of the total stack.
For purposes of summarizing the invention, certain aspects, advantages, and novel features of the invention have been described herein. It is to be understood that not necessarily all such advantages may be achieved in accordance with any one particular embodiment of the invention. Thus, the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein.
In one embodiment, a method of treating a low dielectric constant film fabricated on a substrate includes: delivering a first precursor onto a substrate, the first precursor including a binder solution in an organosol having silicalite particles, the concentration of binder solution in the organosol being equal to a first concentration; baking and subsequently curing the substrate to create a low dielectric constant film from the first precursor; delivering a second precursor onto the first precursor, the second precursor including a binder solution in an organosol having silicalite particles, the concentration of binder solution to organosol in the second precursor being a second concentration that is higher than the first concentration; and baking and subsequently curing the substrate to create a binder-enriched film on top of the low dielectric constant film.
In another embodiment, a method of enhancing adhesion to silicalite-plus-binder films on a substrate includes: spin-coating a standard precursor onto a substrate; spin-coating an enriched precursor on top of the standard precursor on the substrate, the enriched precursor having a higher concentration of binder than the standard precursor; and baking and subsequently curing the substrate to create a film on the substrate, where the film is created by the standard precursor and the enriched precursor.
In still another embodiment, a spin-coater for treating a low dielectric constant film fabricated on a substrate includes a coater, a first and second container, and a dispense arm. The coater is operable to support a substrate, and also operable to rotationally spin the substrate. The first and second containers are operable to hold solutions that are to be dispensed on the substrate. The dispense arm is coupled to the first and second containers, and the dispense arm is operable to dispense the solutions contained in the first and second containers onto the substrate. A single dispense arm can contain a multiplicity of supply lines and nozzles. It is generally preferable to segregate two different materials on a spin coater, and so each container will be attached to a dedicated supply line and nozzle. In one version, both containers contain a solution of silicalite particles and a binder, but the concentration of binder in the solution in the second container is higher than the concentration of binder in the solution in the first container. In another version, the first container contains a silicalite solution and the second container contains a binder.
These and other embodiments of the present invention will also become readily apparent to those skilled in the art from the following detailed description of the embodiments having reference to the attached figures, the invention not being limited to any particular embodiment(s) disclosed.